Avian and murine tumo virus RNA: a) 60-70S RNA of virus released by cells infected with two geneticaly distinct variants (sarcoma & leukemia) will be analyzed by gel electrophoresis and by electron microscopy. Purpose: Do mixed RNA complexes (heterodimers, heterozygotes) exist, which contain both a sarcoma-specific and leukemia-specific subunit? b) The RNA of deletion mutants will be compared to wild-type virus by electrophoresis and oligonucleotide fingerprinting to correlate RNA sequence with genetic function. c) Viral RNA species of infected cells will be compared to virion RNA in size, sequence complexity, and template activity in in vitro translation, to determine whether distinct subsets of viral RNA function as mRNA. d) In vitro translation of wild-type and deletion virus RNAs. 2. Generation of deletion mutants: a) The terminal sequences of wild-type and deletion mutants will be compared b) Redundant sequences will be sought. c) Are the RNAs of all clonal isolates of deletion mutants with the same functional defect exactly the same or different? 3) Completing the genetic map of RSV: a) The gag and pol genes are to be identified in viral recombinants with ts-gag and pol markers. Oligonucleotide mapping will be used to locate the gag and pol sequences in the RNA. b) The map location and function of highly-conserved oligonucleotides of different viral strains will be studied. 4. Oligonucleotide maps of tumor virus recombinant RNAs will be investigated for crossover points to deduce a mechanism of recombination. Recombinant virus proteins will be compared for the same purpose. 5. Murine leukemia-sarcoma virus relationships: The smaller sarcoma-specific RNA and large leukemia-specific RNA subunits will be compared physically and chemically to investigate the known genetic overlaps and to delineate a murine sarcoma gene. 6. The RNAs of defective avian leukemia viruses will be investigated to determine whether a leukemia gene can be defined that differs from the sarcoma gene of RSV.